High impedance accelerometer



June 3, 1958 A. H. IVERSEN' HIGH IMPEDANCE ACCELEROMETER INVENTOR ARTHUR H. IVER SEN W ATTOR Filed Jan. 23, 1956 HIGH IMPEDANCE ACCELEROMETER Arthur H. Iversen, Santa Monica, Calif., assignor to Sylvania Electric Products Inc., a corporation of Messachusetts Application January 23, 1956, Serial No. 560,669

4 Claims. (Cl. 313-72) The invention relates to an accelerometer.

It is an object of the invention to provide a high impedance accelerometer which shall be capable of giving a direct viewing indication of acceleration on an electrical instrument, such as an oscilloscope.

It is a further object of the invention to provide an accelerometer which shall be capable of giving an electric signal from a moving system, such as a guided missile.

It is a still further object of the invention to provide an accelerometer which shall combine with its high impedance, a high sensitivity characteristic to permit of measurement of low accelerations and vibrations.

It is another object of the invention to make the accelerometer rugged, of small size and of few parts.

These and other objects will become apparent after considering the following description and claims along with the accompanying drawing in which:

Fig. 1 shows in cross-section and in diagrammatic form, an accelerometer made in accordance with the invention.

Fig. 2 shows the application of the accelerometer in a simple comparison circuit, and

Fig. 3 is a perspective diagrammatic view showing the relationship of cathode and target anodes.

Referring to the drawings in greater detail, at there is shown an evacuated envelope which may be made of any desired insulating material such as glass. Within this envelope there is supported an electron gun such as a Pierce gun, here shown as comprised of an electric heater 12, rectangular in plan, a concave faced cathode bar 14, a zero potential electrode 16, a grid 18, and an anode 20. Within the tube there are also supported the beam deflecting plates 22 and 24 and the high potential target anode 26, preferably rectangular in form to accord with the rectangular form of the cathode bar.

Each of the electrodes within the tube is connected by a suitable conductor 28 to a suitable lead-in pin 30, as in well known in the art, with the exception that the anode 26 is provided with a rod 32 for its outside electrical connection. The gun is aimed to bombard the anode 26 uniformly with a stream of electrons. However, the anode is normally half occluded by a second target anode 34 of substantially the same size and configuration as anode 26 and arranged parallel to the anode 26 and spaced as close thereto as in conveniently possible. The anode 34 is supported by a long thin resilient metallic cantilever bar 36 running parallel to the electron beam, the bar supporting the anode 34 so that normally it covers one half the face of the anode 26. The end of the bar opposite the anode 34 is supported by the envelope 10 in any desired manner as by a post 38 embedded in the glass post having a forked end 40 welded to an enlarged portion 42 of the bar. A lead 44 welded to the bar provides for external electrical connection to the anode 34.

The bar 36 passes freely through a large opening 46 in the support for the deflection plate 24 to permit bar deflection on acceleration of the tube, the anode 34 under acceleration forces occluding the anode 26 more or less depending on the direction of motion of the tube. The tube is United States Patent 2,837,675 Patented June 3, 1958 mounted in the missile or other moving object so that the bar 36 is transverse to the direction of motion with the long dimension of the anode 34 parallel to the direction of motion.

In circuit use, conventional connections are made to the heater, cathode anodes 16, 20 and deflecting plates 22 and 24. The anodes 26 and 32 are each connected to a positive source of potential via equal resistors 46 with a voltmeter 48 bridging the ends of the resistors to which the leads 32 and 44 are connected. Proper potentials are applied to the plates 22 and 24 to slightly deflect the electron beam should the flow of current in the resistors 46 be unequal, it being assumed that the voltmeter properly reads zero with zero differential voltage applied thereto.

When so adjusted, with no accelerative forces tending to deflect the bar 36, the electron stream will fall on the anodes 26 and 34 in such degree that equal voltage will be impressed across the resistors with no deflection of the voltmeter occurring. On acceleration, the anode 34 will be deflected to cover more or less of the anode 26 to the electron stream, upsetting the opposing voltages on the voltmeter and indicating on the voltmeter the degree of acceleration attained. The voltmeter, if desired, may be calibrated in G rather than in volts so that a direct reading of acceleration may be attained. Other reading instrument such as an oscilloscope calibrated in G may be substituted for the voltmeter.

Having thus described the invention what is claimed is:

I. An accelerometer comprising an electron gun, a fixed target anode in the path of electrons emitted from the gun in position to receive substantially all of the said electrons, a second target anode in the path of the electrons and a rigid envelope mounting the aforesaid elements, acceleration responsive yielding means mounted in said rigid envelope supporting the second anode for movement parallel to the face of the first anode, said second anode being normally in a position to receive substantially only half of the electrons emitted from the gun.

2. An accelerometer comprising an electron gun, a fixed target anode in the path of electrons emitted from the gun in position to receive substantially all of the said electrons, a second target anode in the path of the electrons, and an acceleration responsive cantilever bar parallel to the electron stream supporting said secondanode, said second anode being arranged parallel and close to the first anode and normally occluding half of its surface, and a rigid evacuated envelope enclosing and supporting all of said elements.

3. An accelerometer comprising a rigid, throughout, evacuated envelope enclosing a cathode and two anodes, said two anodes lying in the path of electrons emitted from the cathode, a rigid support Within the envelope for supporting one of said anodes, a rigid support carried by the envelope for the other of said electrodes and acceleration responsive resilient means connecting the rigid,

References Cited in the file of this patent UNITED STATES PATENTS Brett July 21, 1942 Hullegard June 8, 1954 

